Process for coextrusion billets with multiple metallic cylindrical layers by hot isostatic pressing and product

Abstract

Coextrusion billets of two or more concentric metallic layers treated by a hot isostatic pressing (HIP) process in order to form a defect-free bondline between the contiguous touching metal layers. The HIP process can also be applied to extruded or further reduced tubes in order to heal bondline defects.

I claim: 
     
       1. In a process for making an extrusion billet comprising two or more concentric cylindrical layers of zirconium or zirconium alloys with hot isostatic pressing, the improvement which comprises: further treating the billet by hot isostatic pressing under sufficient pressure and proper temperature to form a bond between the metallic layers characterized by improved bonding strength and reduced bondline defects.   
     
     
       2. Tubing produced from the billet process of claim 1 having improved metallurgical bond and substantially free from bondline defects. 
     
     
       3. A process of claim 1 in which said layers comprise at least one zirconium and at least one zirconium alloy. 
     
     
       4. A process of claim 1 for further treatment of extruded tubes. 
     
     
       5. A process of claim 1 wherein the pressure used in the further treatment ranges from 15,000 to 45,000 p.s.i. using argon as the medium. 
     
     
       6. A process of claim 1 wherein the temperature for the further treatment of the high pressure treatment is between 450 degrees C. and 800 degrees C.